This invention concerns conveyors, and more particularly conveyors in which a series of pallets are driven around a closed loop track by a recirculating link chain, parts to be conveyed thereby being carried by the pallets. Such conveyors are commonly used in moving parts through a series of workstations where processes are performed on the parts.
Conveyors are sometimes designed as “accumulator” or asynchronous conveyors, allowing pallets to form a queue at one or more stations by disengaging the drive connection of the pallets to the drive chain so that the drive chain can overrun the queued pallets. Conveyors are also designed to the “synchronous”, in which the pallets always remain in driving engagement with the drive chain and always move in synchronism with the chain.
Many such conveyors arrange the chain to recirculate through a path lying in a vertical plane in which the drive chain has an upper segment along which the parts are advanced, and a return segment lying below the upper segment with end sprockets at either end rotating about a horizontal axis. See U.S. Pat. Nos. 4,757,893 and 5,735,384 for examples of such conveyors.
In another form, the drive chain recirculates along a closed loop path lying in a horizontal plane, which has the advantage of allowing the parts to remain on the pallets through the entire path of the chain recirculation, increasing the number of stations possible, improving the versatility of the conveyor, and enhancing the processing and handling efficiency of the parts.
The parts are usually mounted on an upper horizontal surface on the pallet, but longer parts are sometimes better handled by being vertically suspended thereon.
For that reason, chain conveyors have been devised in which the chain recirculates along a path lying in a horizontal plane and a part can be hung on the side of pallets driven by the chain.
This arrangement is shown in U.S. Pat. Nos. 6,019,214; 6,568,525 and 3,785,475.
In those arrangements, the chain (or a friction band) circulates along a path having only outside turns, as shown in U.S. Pat. No. 6,568,525. Since the return segment can only undergo outside turns, this necessitates an open space between the advance and return conveyor runs if the conveyor routing deviates from a simple straight line, i.e., if one or more of the stations are not aligned. This creates wasted space between advance and return runs of the conveyor which wasted space is a significant disadvantage when installed in the confines of a typical manufacturing facility. It may be desirable for the conveyor to be routed to such a station at such a particular location.
It would be advantageous to be able to route the drive chain and pallets through a path which could include inside turns as the conveyor could be routed to any desired station location while maintaining the advance and return conveyor runs closely spaced to be able to locate various stations anywhere with minimal use of floor space.
In an accumulating conveyor, the need to controllably disengage the pallet from the conveyor drive chain has typically involved complex latching mechanisms which are subject to failure and are costly to fabricate.
It is an object of the present invention to provide a conveyor which includes a pallet drive chain which circulates along a closed loop path lying in a horizontal plane which is able to move pallets around both inside and outside turns for achieving maximum flexibility in locating stations and minimal use of floor space.
It is another object to provide a simplified and reliable arrangement for selectively engaging and disengaging pallets with the conveyor chain while being able to be routed through inside and outside turns.
It is another object to provide a pallet conveyor which can mount parts in either a horizontal on top of the pallets or a vertical orientation on the side of the pallet.